We conducted experiments on specially designed microfluidic chips that generate droplets through a microfluidic ow-focusing approach. The fluid flow in the microfluidic channel produced a shear flow field at low Reyno...We conducted experiments on specially designed microfluidic chips that generate droplets through a microfluidic ow-focusing approach. The fluid flow in the microfluidic channel produced a shear flow field at low Reynolds numbers. The droplets in the microfluidic system exhibited special droplet pattern formations similar to periodic crystal-like lattices because of the competition between shear forces and surface tension. By adjusting the flow rate ratio of the water （droplet phase） to oil （continuous phase） phases and changing the outlet channel widths, the droplets formed monolayer dispersion to double-layer formation to monolayer squeezing when the outlet channel widths were 250 or 300 μm. We also obtained droplets with monolayer dispersion, three-layer arrangements, double-layer squeezing, and monolayer squeezing when the outlet channel width was 350 μm. The outlet channel width was increased to 400 μm, and four-layer arrangements were observed. We also studied the translation of droplet formation, which resulted in a detailed strategy to control drop size and droplet pattern formation for emulsi cation in microfluidic devices. We expect that our strategy can provide theoretical guidance to synthesize dispersion or polydisperse colloid particles.展开更多
Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., ...Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., a porous ceramic membrane substrate, a polyvinylidene fluoride （PVDF） ultrafiltration sub-layer, and a polyamide/polyvinyl alcohol （PVA） composite thin top-layer. The PVDF polymer was east onto the tubular porous ceramic membranes with an immersion precipitation method, and the polyamide/PVA composite thin top-layer was fabricated with an inteffaeial polymerization method. The effects of the sub-layer composition and the recipe in the inteffaeial polymerization for fabricating the top-layer on the structure and performance of composite membranes were systematically investigated. The prepared composite membranes showed a good performance for treating the O/W microemulsions with a mean diameter of about 2.41μm. At the operating pressure of 0.4MPa, the hydraulic permeability remained steadily about 190L·m^-2·h^-1, the oil concentration in the permeate was less than 1.6mg·L^-1, and the oil rejection coefficient was always higher than 98.5% throughout the operation from the beginning.展开更多
In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788), the mixture of Span 85 and xylene or...In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788), the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer, cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed.展开更多
In this study, quaternized chitosan microspheres （QCMS） were prepared and its Cr （VI） removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and t...In this study, quaternized chitosan microspheres （QCMS） were prepared and its Cr （VI） removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. Equilibrium was attained within 50 rain and maximum removal of 97.34% was achieved under the optimum conditions at pH 5. Adsorption data for Cr （VI） uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr （VI） was 39.1 mg.g-a. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, 313 K and 323 K. （AH° = 16.08 kJ.mol- 1;AG° = -5.84 to -8.08 kJ.mo1-1 and AS° = 74.81 J.K-1 .tool-l）. So the positive values of both A/-F and AS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. AG° values obtained were negative indicating a spontaneous adsorp- tion process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could he considered as a potential adsorbent for Cr （V1） in aqueous solutions.展开更多
A study on the membrane coalescence demulsification was carried out with four working systems of water/n-butyl alcohol, water/n-octanol, water/30% TBP(in kerosene) and water/kerosene. The membranes made of polytetrafl...A study on the membrane coalescence demulsification was carried out with four working systems of water/n-butyl alcohol, water/n-octanol, water/30% TBP(in kerosene) and water/kerosene. The membranes made of polytetrafluoroethylene (PTFE) with 1.0μm pore size were used. The results indicated that the excellent demulsification efficiency for emulsions with various oil contents was obtained. A conductivity probe was used to study the demulsification mechanism. An electrode probe was designed and used to determine the oil content near the membrane surface. The obtained data showed that the oil content in the permeated stream was much higher than that in the feed emulsion. A physical mechanism to explain the membrane demulsification was put forward.展开更多
The electro-polymerization behavior of aniline in reverse(W/O) microemulsion was investigated. The experiment results show that the cyclic voltammetry polymerization behavior of aniline in W/O microemulsion is differe...The electro-polymerization behavior of aniline in reverse(W/O) microemulsion was investigated. The experiment results show that the cyclic voltammetry polymerization behavior of aniline in W/O microemulsion is different from that in aqueous solution remarkably. With the increase of scan cycle, the oxidation potential shifts positively and the reduction potential shifts negatively, i.e., the redox potential difference increases. H+ apparent concentration affects the aniline polymerization evidently. When H+ concentration is lower than 0.08 mol/L, the electro-polymerization of aniline is difficult. With the increase of H+ concentration, the polymerization current of aniline increases gradually. Only when H+ concentration is high enough(0.5 mol/L), aniline can be well electro-polymerized. Moreover, under the same condition, the aniline polymerization current in W/O microemulsion is higher than that in aqueous solution. The scanning electron microscopy image shows that the deposited polyaniline(PANI) has uniform fiber morphology with diameter of about 100 nm. Further study result suggests that the electrochemical activity of the PANI in HCl is similar to that of the PANI prepared in aqueous solution.展开更多
Based on viscous drag-induced breakup mechanism, a simple model was proposed to predict the dripping droplet size as a function of controllable parameters in flow focusing micro devices. The size of thread before brea...Based on viscous drag-induced breakup mechanism, a simple model was proposed to predict the dripping droplet size as a function of controllable parameters in flow focusing micro devices. The size of thread before breakup was also investigated through laminar flow theory. Experiments and numerical simulations by VOF are carried out simultaneously to validate the theoretical analysis, showing that droplet size decreases rapidly with the increase of the flow rate ratio and capillary number.展开更多
Polymer nanoparticles were prepared in the methyl methacrylate (MMA)/buty lmethacrylate (BA) emulsion copolymerization process by a modified microemulsion copolymerization method. 2-Hydroxyethyl methacrylate(HEMA), ac...Polymer nanoparticles were prepared in the methyl methacrylate (MMA)/buty lmethacrylate (BA) emulsion copolymerization process by a modified microemulsion copolymerization method. 2-Hydroxyethyl methacrylate(HEMA), acrylate (AA) and methyl acrylate (MAA) were used as reactive cosurfactants. With this process high polymer: surfactant weight ratios (40:1 or greater),relatively concentrated (~30wt. %) latexes and small (~60nm) particle diameters were obtained.Properties of the latexes were characterized by TEM, DSC, dynamic light scattering, and IR spectroscopy.展开更多
Polypyrrole (PPy) films were prepared by multi-potential steps polymerization in an aqueous pyrrole solution, with lithium perchlorate and oxalic acid as supporting electrolytes. Morphology and structure of PPy films ...Polypyrrole (PPy) films were prepared by multi-potential steps polymerization in an aqueous pyrrole solution, with lithium perchlorate and oxalic acid as supporting electrolytes. Morphology and structure of PPy films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical behaviors of PPy films were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that multi-potential steps polymerization improves the conductivity of PPy films and large polymer films can be peeled off easily from the electrode without cracking. Lithium perchlorate and oxalic acid provide appropriate dopants for PPy polymerization. It was observed that the polymerization time and the current density have a crucial influence on the surface morphology of PPy films. Smooth and compact PPy films could be generated under long polymerization time and low current density. Multi-potential steps polymerization decreases the occurrence of peroxidation, which improves the conductivity of PPy films. The parameters for multi-potential steps polymerization have been optimized.展开更多
Microparticles have a demonstrated value for drug delivery systems. The attempts to develop this tech- nology focus on the generation of featured microparticles for improving the function of the systems. Here, we pres...Microparticles have a demonstrated value for drug delivery systems. The attempts to develop this tech- nology focus on the generation of featured microparticles for improving the function of the systems. Here, we present a new type of microparticles with gelatin methacrylate （GelMa） cores and poly（L-lactide-co-glycolide） （PLGA） shells for syn- ergistic and sustained drug delivery applications. The mi- croparticles were fabricated by using GelMa aqueous solu- tion and PLGA oil solution as the raw materials of the mi- croflnidic double emulsion templates, in which hydrophilic and hydrophobic actives, such as doxorubicin hydrochloride （DOX, hydrophilic） and camptothecine （CPT, hydrophobic）, could be loaded respectively. As the inner cores were poly- merized in the microfluidics when the double emulsions were formed, the hydrophilic actives could be trapped in the cores with high efficiency, and the rupture or fusion of the cores could be avoided during the solidification of the micropar- ticle shells with other actives. The size and component of the microparticles can be easily and precisely adjusted by ma- nipulating the flow solutions during the microfluidic emulsi- fication. Because of the solid structure of the resultant mi- croparticles, the encapsulated actives were released from the delivery systems only with the degradation of the biopolymer layers, and thus the burst release of the actives was avoided. These features of the microparticles make them ideal for drug delivery applications.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.20934004 and No.91127046） and the National Basic Research Program of China （No.2012CB821500 and No.2010CB934500）.
文摘We conducted experiments on specially designed microfluidic chips that generate droplets through a microfluidic ow-focusing approach. The fluid flow in the microfluidic channel produced a shear flow field at low Reynolds numbers. The droplets in the microfluidic system exhibited special droplet pattern formations similar to periodic crystal-like lattices because of the competition between shear forces and surface tension. By adjusting the flow rate ratio of the water （droplet phase） to oil （continuous phase） phases and changing the outlet channel widths, the droplets formed monolayer dispersion to double-layer formation to monolayer squeezing when the outlet channel widths were 250 or 300 μm. We also obtained droplets with monolayer dispersion, three-layer arrangements, double-layer squeezing, and monolayer squeezing when the outlet channel width was 350 μm. The outlet channel width was increased to 400 μm, and four-layer arrangements were observed. We also studied the translation of droplet formation, which resulted in a detailed strategy to control drop size and droplet pattern formation for emulsi cation in microfluidic devices. We expect that our strategy can provide theoretical guidance to synthesize dispersion or polydisperse colloid particles.
基金Supported by the Trans-century Training Programme Foundation for the Talents by the Ministry of Education of China (No.2002-48).
文摘Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., a porous ceramic membrane substrate, a polyvinylidene fluoride （PVDF） ultrafiltration sub-layer, and a polyamide/polyvinyl alcohol （PVA） composite thin top-layer. The PVDF polymer was east onto the tubular porous ceramic membranes with an immersion precipitation method, and the polyamide/PVA composite thin top-layer was fabricated with an inteffaeial polymerization method. The effects of the sub-layer composition and the recipe in the inteffaeial polymerization for fabricating the top-layer on the structure and performance of composite membranes were systematically investigated. The prepared composite membranes showed a good performance for treating the O/W microemulsions with a mean diameter of about 2.41μm. At the operating pressure of 0.4MPa, the hydraulic permeability remained steadily about 190L·m^-2·h^-1, the oil concentration in the permeate was less than 1.6mg·L^-1, and the oil rejection coefficient was always higher than 98.5% throughout the operation from the beginning.
文摘In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788), the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer, cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed.
基金Supported by the National Key Basic Research Development Plan(No.2013CB632602)the National Natural Science Foundation of China(No.21306198)
文摘In this study, quaternized chitosan microspheres （QCMS） were prepared and its Cr （VI） removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. Equilibrium was attained within 50 rain and maximum removal of 97.34% was achieved under the optimum conditions at pH 5. Adsorption data for Cr （VI） uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr （VI） was 39.1 mg.g-a. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, 313 K and 323 K. （AH° = 16.08 kJ.mol- 1;AG° = -5.84 to -8.08 kJ.mo1-1 and AS° = 74.81 J.K-1 .tool-l）. So the positive values of both A/-F and AS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. AG° values obtained were negative indicating a spontaneous adsorp- tion process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could he considered as a potential adsorbent for Cr （V1） in aqueous solutions.
基金Supported by the National Natural Science Foundation of China(No.29976021).
文摘A study on the membrane coalescence demulsification was carried out with four working systems of water/n-butyl alcohol, water/n-octanol, water/30% TBP(in kerosene) and water/kerosene. The membranes made of polytetrafluoroethylene (PTFE) with 1.0μm pore size were used. The results indicated that the excellent demulsification efficiency for emulsions with various oil contents was obtained. A conductivity probe was used to study the demulsification mechanism. An electrode probe was designed and used to determine the oil content near the membrane surface. The obtained data showed that the oil content in the permeated stream was much higher than that in the feed emulsion. A physical mechanism to explain the membrane demulsification was put forward.
基金Projects(51071067,21271069,20673036,J1210040,50473022) supported by National Natural Science Foundation of ChinaProject(2013GK3015) supported by the Science and Technology Program of Hunan Province,China
文摘The electro-polymerization behavior of aniline in reverse(W/O) microemulsion was investigated. The experiment results show that the cyclic voltammetry polymerization behavior of aniline in W/O microemulsion is different from that in aqueous solution remarkably. With the increase of scan cycle, the oxidation potential shifts positively and the reduction potential shifts negatively, i.e., the redox potential difference increases. H+ apparent concentration affects the aniline polymerization evidently. When H+ concentration is lower than 0.08 mol/L, the electro-polymerization of aniline is difficult. With the increase of H+ concentration, the polymerization current of aniline increases gradually. Only when H+ concentration is high enough(0.5 mol/L), aniline can be well electro-polymerized. Moreover, under the same condition, the aniline polymerization current in W/O microemulsion is higher than that in aqueous solution. The scanning electron microscopy image shows that the deposited polyaniline(PANI) has uniform fiber morphology with diameter of about 100 nm. Further study result suggests that the electrochemical activity of the PANI in HCl is similar to that of the PANI prepared in aqueous solution.
基金Supported by the National Natural Science Foundation of China(50876100)the Grade A Technology Development Foundation of USTC(ZC9850340103)
文摘Based on viscous drag-induced breakup mechanism, a simple model was proposed to predict the dripping droplet size as a function of controllable parameters in flow focusing micro devices. The size of thread before breakup was also investigated through laminar flow theory. Experiments and numerical simulations by VOF are carried out simultaneously to validate the theoretical analysis, showing that droplet size decreases rapidly with the increase of the flow rate ratio and capillary number.
基金CEM Foundation For N & T Joint Academy (Chinese Education Ministry Foundation for Nankai University and Tianjin University Joint Academy)
文摘Polymer nanoparticles were prepared in the methyl methacrylate (MMA)/buty lmethacrylate (BA) emulsion copolymerization process by a modified microemulsion copolymerization method. 2-Hydroxyethyl methacrylate(HEMA), acrylate (AA) and methyl acrylate (MAA) were used as reactive cosurfactants. With this process high polymer: surfactant weight ratios (40:1 or greater),relatively concentrated (~30wt. %) latexes and small (~60nm) particle diameters were obtained.Properties of the latexes were characterized by TEM, DSC, dynamic light scattering, and IR spectroscopy.
基金supported by the National Basic Research Program of China ("973"Program) (Grant No. 2011CB935701)the National Science Foundation for Post-doctoral Scientists of China (Grant No. 20100480251)
文摘Polypyrrole (PPy) films were prepared by multi-potential steps polymerization in an aqueous pyrrole solution, with lithium perchlorate and oxalic acid as supporting electrolytes. Morphology and structure of PPy films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical behaviors of PPy films were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that multi-potential steps polymerization improves the conductivity of PPy films and large polymer films can be peeled off easily from the electrode without cracking. Lithium perchlorate and oxalic acid provide appropriate dopants for PPy polymerization. It was observed that the polymerization time and the current density have a crucial influence on the surface morphology of PPy films. Smooth and compact PPy films could be generated under long polymerization time and low current density. Multi-potential steps polymerization decreases the occurrence of peroxidation, which improves the conductivity of PPy films. The parameters for multi-potential steps polymerization have been optimized.
基金supported by the National Natural Science Foundation of China (21473029 and 51522302) the NSAF Foundation of China (U1530260)+4 种基金the National Science Foundation of Jiangsu (BK20140028) the Program for New Century Excellent Talents in Universitythe Scientific Research Foundation of Southeast UniversityFoundation of Jiangsu Cancer Hospital (ZN201609)Beijing Medical Award Foundation (YJHYXKYJJ-433)
文摘Microparticles have a demonstrated value for drug delivery systems. The attempts to develop this tech- nology focus on the generation of featured microparticles for improving the function of the systems. Here, we present a new type of microparticles with gelatin methacrylate （GelMa） cores and poly（L-lactide-co-glycolide） （PLGA） shells for syn- ergistic and sustained drug delivery applications. The mi- croparticles were fabricated by using GelMa aqueous solu- tion and PLGA oil solution as the raw materials of the mi- croflnidic double emulsion templates, in which hydrophilic and hydrophobic actives, such as doxorubicin hydrochloride （DOX, hydrophilic） and camptothecine （CPT, hydrophobic）, could be loaded respectively. As the inner cores were poly- merized in the microfluidics when the double emulsions were formed, the hydrophilic actives could be trapped in the cores with high efficiency, and the rupture or fusion of the cores could be avoided during the solidification of the micropar- ticle shells with other actives. The size and component of the microparticles can be easily and precisely adjusted by ma- nipulating the flow solutions during the microfluidic emulsi- fication. Because of the solid structure of the resultant mi- croparticles, the encapsulated actives were released from the delivery systems only with the degradation of the biopolymer layers, and thus the burst release of the actives was avoided. These features of the microparticles make them ideal for drug delivery applications.
